Questions about my outdoor wood boiler...

Finally got fed up with the high propane costs for my indoor propane boiler and went and bought an outside wood boiler and all the necessary parts to tie it into my indoor propane boiler. This weekend I set the boiler, buried the line and hooked it all up all excited to finally have a warm house with no heating costs. I have spent the past 4 days trying to figure out why it wont even stabilize my house temp lil own heat it up. The outside boiler is a 198 gallon non pressurized boiler made by Midwest(now called synergy). I set it 70 ft from my house and buried the line 4 ft deep..the supply line comes into the basement wall to my circ. pump ( at lowest point), then continues to my domestic hot water brazed plate exchanger(20 plate), exits the heat exchanger and enters a second heat exchanger for my indoor propane boiler(on the return line from both zones, 40 plate), then leaves the basement and goes back to the owb. if I turn my circ pump off the owb will get upto temp (180 deg.) but as soon as I turn it on I start slowly losing temp. The blower and solenoid are working fine and the chimney( which only comes out 1 ft) is clean....From the owb to the second heat exchanger where my baseboard loop comes through I only have a 4 degree heat loss. Why cant I keep this water heated up? My house is a 1600 sq. ft log home and this boiler previously heated a 3000 sq ft house along with its basement and garage effortlessly and is rated for a 5000 sq ft home(which I know varies depending on insulation). my parents house is 2500 sq ft and they use a smaller owb to heat theres so why is this not working for me..What is causing me to lose temp so fast so that my baseboards cant get hot enough to heat with? thnx for any help ahead of time

 

Are the pipe runs insulated?
Could there be air in the lines?
Is you wood wet?
Is the owb setup properly?

Lots of questions since this is a new install.
Can you include a few pics of how the outdoor boiler is tied into the house.

 

What size PEX did you use? and ditto the question on insulation...

Also ditto the wet / green wood, you would be amazed at how much heat is lost up the chimney burning wet / green wood.

What pump are you using to circulate between boiler and home?

 

You are saying that the water temp at the wood boiler before going underground for 70 feet is 4°F higher than the EXIT temp of the heat exchanger on the water heater?

What is the difference in temp between the inlet and the outlet on the 2nd HX ?

What is the difference in temperature between the EXIT of the 2nd HX and the return at the OWB after it comes back out the ground?

I believe you are saying that the circ pump for the OWB is in the house, not at the OWB?

 

What is the math formula to determine the heat loss through the pipes to the ground from an outdoor boiler to the house? Thanks in advance .

 

It could be calculated if one knew the flow and the delta T ... getting the flow number is the hard part...

 

yes, the pipe runs are insulated 1" pex. we have bled the line 3 times to be sure. using slabs of seasoned ash from a mill up the road to heat boiler as of now to ensure our fire is hot. Had a very experienced heating contractor here today and he says everything is hooked up correctly and is dumbfound. when not circulating we can get boiler to 180 deg. as soon as we turn on the circ pump we start losing temp. is there even anything that can go wrong inside the boiler? isn't it just a water jacket?

 

Please provide the model number of the outside boiler...we will need to see if we can find the install manual for review

 

1" insulated pex, dry ash slabs, have tried 2 different pumps on all 3 speed settings a Wilo typ sytar S 21 FX and a Bell & Gossett NRF-36

 

correct on the first question, Not sure of the answer to your second question as I have no way to measure the heat there. yes the pump is currently in the house because I was told it needed to be at the lowest point, however I did previously have it on the boiler with the same results

 

I do not know the model number but the boiler is a Midwest with 198 gallon water jacket, 36" deep firebox. I have searched ans been able to come up with an install manual

 

You're going to have to find a way to get reasonable accurate temperatures at the points I mentioned. At least we would have some data to chew on rather than wild azz guesses...

Using the temperature data we can at least come up with some theories regarding flow and where the heat is going.

I wouldn't mind seeing pictures also, in spite of the fact that a 'heating professional' said it was all good.

 

I will try and get a pyrometer from work tomorrow and get back to you with some accurate temps

 

Looks like a Classic CL5036, 250,000 max btu, 30 deep firebox.
Does it have a barn style roof?

 

How do you know the outdoor stove is fully filled with water?
Could not find any info on Midwest website, so I looked at central boiler website instead.

 

One last question, do you have a thermostatic valve to allow the stove water to come up to temperature before trying to steal the hot water away for the other heating purposes?
The circulator should be moving water from the wood boiler back to itself until the entire wood system is hot, then the thermostatic valve will start to allow the hot water into the other heat transfer items you discussed in your initial post.

 

there is a site glass for the water level

 

When plumbing in the plate exchangers, did you happen to install bypass valves for each plate?
If so, bypass both plate exchangers, fire up the owb and keep the circulator running. Does the system heat up?

Pics would be helpful....

 

I have an owb hooked up to an indoor propane boiler with 2 hot water baseboard zones. They are 2 different systems connected with a brazed plate heat exchanger. The owb is a non-pressurized system where the propane boiler is pressurized. im curious of the correct way to bleed air on the owb loop so i can ensure proper heat transfer and also curious what the normal or max heat loss should be from my owb supply to where it returns after flowing through my lines and heat exchanger. Also, what will happen if i have an air bubble in HX? I couldnt get my owb to temp when flowing through it so i bypassedit and the owb heated up. According to everything ive seen online i have the HX hooked up correctly.

 

Hi Admiral, there is no need to start a new thread, please continue to use the first one you started for your wood boiler..................

By 'heat loss' I think you mean 'temperature drop'. The system should probably be designed for no more than I would say 40°F between the supply and return at the OWB. If you are getting MORE than this it indicates either insufficient flow, or you are removing too many BTU from the flow that exists.

If the water into the OWB side of your HX is HOT and coming out is COLD it means that you are removing heat from the water and transferring it to the water in the home system.

We need temperature data on the water that is entering the HX from the OWB and exiting, and ALSO the temperature of the water entering and exiting the HX from the home system.

If you have an air bubble in the HX that is blocking flow then the OWB should have no trouble heating up because you aren't taking BTU out of it due to no flow... so I believe that you have flow based on what you have told us so far.

Meaning that you are running it in 'counter-flow'... the HOT SUPPLY from the OWB is entering on the same side that the COOL RETURN from the home system is, and vice versa on the other end? In other words, the flow on each side is opposite the other, correct?

What we need is DATA... we need to 'follow the heat' to see where it's going.

Need temperature data as follows:

HOT SUPPLY out of OWB (AT the OWB)

RETURN TO OWB (also at the OWB)

Entering temp to first HX, exiting temp at first HX, temps on OTHER side of first HX

Ditto for the second HX.

The heat is going SOMEWHERE and the only way to determine where is by taking temperatures.

 

Unfortunately, I wasn't able to get temp. readings today either as the pyrometer I brought home malfunctioned. However, I heated my house up with the fireplace and shut off my hydronic baseboard loops so they weren't circulating through the HX. My owb came right upto temp and I kept it there with ease, burning very little wood all day. Late this afternoon I turned my baseboard zones back on and started circulating. As soon I did that my boiler temp started falling off. I have a hard time believing it but maybe my owb simply is undersized? It has a barrel style firebox that is 36" and a 200 gallon water jacket and is rated for 5000 sq. ft. Was previously having no problems heating a well insulated 3000 sq ft. home and its small garage with forced air. I'm 1650 sq. ft log home(not insulated as well but not terrible). Am I simply just too small? after I started circulated my pressurized loop I could feel a temp drop from the supply line to the return line of the HX on my owb loop where it had been steady all day before I started calling for heat.

 

Pictures of the plumbing access panel on the outdoor boiler please.
We are wondering if the water connections are made properly on the outdoor boiler. If not plumbed properly, you may not get the cross flow NJ was speaking of.

Inside house pics too.
You ran the stove with circulator running all day and the system heated up. This is good, but you were not taking away any BTUs because you were not circulating your baseboard water. You could try starting the baseboard circulator until the outdoor boiler temp drops, then stopping baseboard circulator outdoor boiler temp get back up to temp, then restart the baseboard circulator, and repeat those steps until the outdoor boiler can maintain the house temp....this would be just to prove the point that the outdoor boiler can hold house at temp.

Try to get some temp readings so we can understand temp drops on each HX.

Did you install a thermostatic valve?

 

Oh, and I do not think the owb is undersized. If anything, you should be sweating you bottom off and walking around in your birthday suit due to the heat!

 

Just wanted to let everyone know that I got the boiler figured out. I believe I had an air pocket in my second heat exchanger. I tried burping the exchanger with a 1" valve downstream and blew a sharkbyte fitting. After fixing it I tried to bleed the system with the circ pump running and got no water beyond the exchanger..played with it a while and eventually got a good flow. Boiler has been running great since. The only complaint I have is I that when the blower goes off if the fire is in the back or there is any green wood at all, I lose temp and it cant get back up. My folks burn green wood in theres all the time with no problems and Ive been running the boiler hard just to avoid the water cooling too much (180-190).I checked the model of my blower and found out it is a 50 cfm blower, where as compared to my parents is a 146 cfm blower. Is this my problem that just my blower is undersized right from the manufacturer? seems to be blowing good so I don't think there's anything wrong with it.Also, this particular boiler has the chimney run all the way down through the firebox and starts just about 4" off the bottom. thnx guys

 

Hi Admiral,
Was not sure if you were going to get back and let us know what you had found.

If your heat exchanger plates were in series with the circulator, it does not make sense when you started the circulator, your water temp would fall due to an air bubble. If in series and the circulator was at the lowest point, an air bubble would have been pushed out and pushed into the outdoor boiler tank and vented.

I do not think your issue is solved. Something else is still not right. You should not be having water temp drop issues, especially if your hydronic water temp is high and the blower fan shuts off.

Please post some pics and show us how things are plumbed inside and out. Also get some temp measurements in and out of the plate exchangers.

 

Here is an interesting way to assess heat loos in an insulated PEX

DTP Heat Loss Calculator for Thermoflex Insulated Pipe - Professional Services - Solutions Insulated PEX

It is product's specific, but I think this can be used for any similar product. Takes into account climate, soil conductivity, depth etc

 

In my opinion the pipes to and from the boiler are not insulate enough or the insulation has absorbed water and your heating the earth. Once the groun is heated up the boiler will deliver hotter water to the house and it will seem to be working properly , but in fact will be very inefficient and require lots of wood.